Skyscrapers/Transcript
Transcript Text reads: The Mysteries of Life with Tim & Moby Tim, looks at a map as he and Moby walk in New York City. Moby points up. MOBY: Beep. Moby and Tim look up at the Empire State Building. TIM: Yep, that's the one. Let's go. Moby and Tim go inside the building and wait for the elevator. The elevator doors open and they step inside. Tim reads from a typed letter. TIM: Dear Tim and Moby, How do tall buildings stay up? From, B.D. That's a good question. Every building has to deal with three main forces working against its staying up: gravity, compression, and tension. An image shows a building. An arrow points down, indicating gravity. TIM: Earth's gravity pulls every mass on its surface toward the center of the Earth. That means that any structure we put up has to resist a force that wants to pull it down. No matter what kind of structure you're looking at, the forces of compression and tension are at work. Moby squeezes the ends of a loaf of bread. TIM: Compression causes material to push together. An image of the building shows a downward arrow at the top, indicating compression. An animation shows the building's support columns being pushed down, making the building shorter. TIM: The buildings we see every day have to handle compression from the weight of the structure. For example, the column supports in this skyscraper are constantly being pushed down by the load above. Tension is the opposite of compression: it's a force that pulls material apart. Moby stretches the loaf of bread. TIM: When material is in tension, it gets longer. An animation shows two horizontal arrows pointing out from the sides of the building, indicating tension. The building gets shorter and wider from the combined forces of compression, gravity, and tension. TIM: The weight of each floor in this skyscraper makes the beam want to pull apart. MOBY: Beep. TIM: But the building doesn't pull apart, or buckle, or fall. So what's going on? For a structure to stay up, it has to have the necessary support to keep these forces in check. An image shows a skyscraper's grid-like support structure. TIM: In skyscrapers, a grid of beams and columns forms a skeleton for the building. The skeleton is called a superstructure, and it makes it so that the skyscraper can distribute these forces and hold up its weight. An image shows a steel beam. TIM: Superstructures are made of steel, a material that is relatively lightweight, and good under compression and tension. An image shows the superstructure’s vertical steel columns. Arrows indicate the force of compression. TIM: Steel columns take on the load of the building. They are under compression. An image shows horizontal steel beams. Arrows point right and left indicating the forces of tension. TIM: Steel beams bind the columns to keep tension from pulling the skeleton apart and prevent forces like wind from damaging the structure. An image shows arrows at the base of the superstructure indicating compression forces. TIM: Even so, all that downward force needs somewhere to go. It's the job of the building's foundation to distribute that force without sinking into the ground. A lot of planning goes into designing a building's structure. An image shows a diagram of the Empire State Building’s elevator. TIM: Even this elevator column here acts as a support. The elevator doors open. An image shows the Empire State Building in silhouette. TIM: It's a little nerve-wracking being at the top of something so, so tall. Tim and Moby are on the skyscraper's observation deck. There is a viewfinder in front of them. TIM: But this is totally worth it. MOBY: Beep. Tim looks into the viewfinder. TIM: Hey, Moby, look at that! And, hey, Moby, look! Look at that! Woah, look at that! Woah, look at that. Category:BrainPOP Transcripts